This is a proposal for a continuation of the Midcareer Investigator Award in Patient-Oriented Research (K24) for Lee H. Harrison, MD, at the University of Pittsburgh. The principal aims of the award are to (1) continue to provide mentorship in patient-oriented research to junior faculty, graduate students, and infectious diseases fellows, (2) continue to provide leadership and direction to the Infectious Diseases Epidemiology Research Unit (IDERU) and Public Health Infectious Diseases Laboratory (PHIDL) at the University of Pittsburgh, and (3) support Dr. Harrison's research on the epidemiology and molecular epidemiology of serious bacterial pathogens. As with the first five years of the award, a major focus of the next five years will be to provide mentorship to infectious diseases fellows, graduate students, and junior faculty members. This will be accomplished by having dedicated time for mentorship and by making available substantial resources to trainees, including: the resources of the IDERU, which has a broad research portfolio of clinical, epidemiologic and molecular epidemiologic studies of bacterial diseases, and PHIDL, a cutting-edge molecular epidemiology laboratory, at the University of Pittsburgh; two NIH Fogarty International Center research training grants, one on the epidemiology and molecular epidemiology of serious bacterial diseases and another on HIV/AIDS; and the resources of the CDC-funded Maryland Active Bacterial Core Surveillance (ABCs) project, which is based at Johns Hopkins University and led by Dr. Harrison. One of the many studies that will be conducted during the award period includes a project entitled, Phase IV Study of Effectiveness Of Tetravalent (A, C, Y, W-135) Meningococcal Conjugate Vaccine , a post-licensure study to measure the effectiveness of the new tetravalent meningococcal conjugate vaccine (MCV4). This will be a matched case-control effectiveness study which has the primary aim of determining overall effectiveness of MCV4 against vaccine preventable serogroups. Secondary aims of the study are to determine the serogroup-specific effectiveness of MCV4 against the two common vaccine preventable meningococcal serogroups in the United States, serogroups C and Y.